Avast 6 "Malicious URL Blocked"

As I was browsing Google Images for a new desktop background, I had just typed in the phrase when Avast pops up a notification saying "Malicious URL Blocked" which apparently contained Malware. Running Google Chrome and being told it was safe, I was shocked. To be on the safe side, I uninstalled and re-installed chrome and ran a full scan with Avast. Avast had found no viruses so I decided to continue browsing. I searched once more for an image and again Avast pops a notification saying "Malicious URL Blocked!" Scratching my head, I used google images to find another image and yet again "Malicious URL Blocked!" So, whenever I use google images, a malicious URL pops up. What does this mean? Is there a virus on my computer? I'm currently running another full scan with MalwareByte's Anti-Malware to try and find the source and I'll get back to you on what I find but should I be worried? I didn't access any site, I was just on google images. However, if I search something like "Pig" or "Cow" or "Horse" Avast continues to display that a Malicious URL was blocked.

I'm also running Windows 7 64-bit

*EDIT* MalwareByte's had picked up something. After removing it, I once again ran a full system scan with Avast and re-installed Google Chrome. So far so good.